Interior trim components of the above mentioned general type, such as door trim panels and dashboards for automobiles, as well as methods and apparatus for forming such trim components are generally known in the art. However, the known products, methods and apparatus all suffer disadvantages, which the industry has long felt a need to overcome or improve upon. The automobile industry has come to require a "soft-touch" characteristic for high quality trim components. In other words, the surface of the trim components must feel soft or resilient, and not hard or rigid, to the touch. This requirement arises from impact protection considerations, and even more simply from consumer preferences. In order to provide such a soft-touch characteristic, known trim components typically comprise a form-stable substrate, a soft foam layer that provides the "soft-touch", and a decorative cover film that will form the exposed surface of the trim component. There are several known methods for forming such multi-layered laminated or composite trim panels.
A first widely employed method involves forming the cover film of a polyvinylchloride material for example, forming the substrate of a synthetic plastic material such as ABS plastic or polypropylene, and then back-foaming a polyurethane foam onto the backside of the decorative cover film, i.e. between the cover film and the plastic substrate. After the polyurethane foam injection step, the three-layered, formed material is cut into the required final shape. The product resulting from this foam injection or back-foaming method includes a polyurethane foam layer that has a substantially uniform foam density, and that can have a substantially uniform thickness over the entire trim component if desired, so that the trim component has a soft-touch characteristic and an impact energy absorbing characteristic over its entire surface, including over the edges or corners thereof.
The back-foaming method, however, suffers distinct disadvantages. Most importantly, the back-foaming or foam injection step requires significantly longer and even a multiple of the time required for carrying out the other product forming steps in the total product forming cycle. Thus, the foaming step is a production bottleneck. Furthermore, the foaming equipment and materials require a relatively high capital and material investment. Also, the finished products comprise a mixture of different synthetic materials firmly bonded together, and thus these products cannot be easily broken down and recycled.
According to another known method, a cover sheet including a cover film and a foam layer is laminated, using an interposed adhesive layer, onto a pre-formed wood fiber or synthetic plastic substrate. The cover film and foam layer are molded or formed onto the pre-formed substrate using heat and pressure in a molding apparatus. Due to the adhesive layer, it has been found that the cover film and foam layer can slip or shift and thus cause wrinkling or bunching of the cover sheet when the molding lamination is carried out. Furthermore, the cover film and the foam layer are necessarily pulled and stretched to a greater extent, and thus caused to become thinner, at areas of the pre-formed substrate having sharply curved edges or corners. Thus, in the finished product, the cover film and foam layer are substantially thinner in the areas of sharp radius edges and corners as well as protruding areas or deeply recessed areas than in the flat surface areas of the trim component. As a consequence, the corners, edges and strongly contoured portions of the trim component do not provide an adequate soft-touch characteristic, i.e. these areas feel relatively hard or rigid to the touch.
It is also known to laminate and mold the trim component in a so-called one-shot method, in which the substrate, the foam layer, and the cover film are initially provided as webs of material having a substantially constant thickness or cross-section, and are then laminated together and formed or molded in three-dimensions in a single molding operation. Disadvantageously in this method, the foam layer and the cover film are heated to a relatively high molding temperature and therefore become soft and deformable during the laminating and molding process. As a result, the cover film and foam layer are significantly thinned at all of the corners, edges, sharply curved radii and strongly contoured areas of the trim component. Similarly, the substrate itself is thinned due to the molding process at these areas. Consequently, the substrate, the foam layer, and the cover film are all thinner and harder at the corners, edges and sharply curved radii of the finished product. While an adequate soft-touch effect can be achieved on the flat surface areas, it cannot be achieved at the corners, edges and sharply contoured areas. The fiber structure or grain character of the substrate may even show through the surface of the thinned cover film in these areas.
It is also known to use injection molded synthetic material substrates for standard automobile dashboards and other trim components. A cover film is simply glued or laminated onto the previously injection-molded substrate. A disadvantage of such trim components is that they are hard and do not offer the desired soft-touch characteristic, and furthermore, such trim components can shatter or splinter rather than absorbing energy in impact situations.